Magnetogasdynamic electric generator



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Aug. 23, 1966 J. c. CROWN ET AL 3,268,746

MAGNETOGASDYNAMIC ELECTRIC GENERATOR Filed Dec. 29, 1960 /NVE'NTOES JOHNCONRAD CROWN EDWARD A. P/NSLEV BY @fwd fz/Lw@ ArolP/VEV United StatesPatent O 3,268,746 MAGNETOGASDYNAMIC ELECTRIC GENERATOR John ConradCrown, West Hartford, Conn., and Edward A. Pinsley, Cambridge, Mass.,assignors to United Aircraft Corporation, East Hartford, Conn., acorporation of Delaware Filed Dec. 29, 1960, Ser. No. 79,405 8 Claims.(Cl. S10- 11) This invention relates to magnetogasdynamic electricgenerators and more particularly to generators orf this type wherein theworking fluid is ionized substantially only in the region of electricalgeneration.

In magnetogasdynamic electric generato-rs wherein an ionized workingfluid is passed through a magnetic field to produce electric current, aproblem arises as to a shortcircuiting of the current in regionsimmediately upstream or downstream of the generating region therebyintroducing losses and reducing the efiiciency of the device.

It is, therefore, a primary object of lthis invention to provide amagnetogasdynamic electric generator in which the short-circuit losses4are minimized or completely avoided.

It is a further obje-ct of this invention to provide a generator of -thetype described wherein the fluid is appreciably ionized only while owingthrough the generating region.

It is a still further object of this invention to provide a generator ofthe type described in which an essentially non-ionized fluid isintroduced to the generating region and is ionized by some seedingmaterial. The degree oi ionization and hence the electricalc-onductivity of the working liuid is substantially reduced by theintroduction of a quenching fluid in the vicinity of the end of thegenerating region.

These and other objects of this invention will become readily apparentfrom the following detailed description ofthe drawing in which:

FIG. l is a schematic illustration of a typical magnetogasdynamicelectric lgenerator of the prior art;

FIG. 2 is a `schematic illustration of an improved generator accordingto this invention;

FIG. 3 is an enlarged portion of FIG. 2 illustrating the wall injectionapparatus; and

FIGS. 4 and 5 are side-sectional views of a typical nozzle dor internalinjection in the generator.

Referring to FIG. l a typical prior art magnetogasdynamic electriclgenerator is generally indicated at as having an inlet 12 for flowing ahigh-temperature ionized working fluid. The fluid flows through agenerating region which has suitable means (not shown) for passing amagnetic eld generally -indicated by the numeral 14 through thegenerator. The magnetic field is crossed or cut by the electricallyconducting flow so as to generate an electrical current in a directionshown by the arrows 16. Suitable electrodes 18 and 20` collect this-generated electrical current and conduct it to a suitable load 22.

In an arrangement such as that shown in FIG. 1, it has been known thatshort-circuit paths are encountered such as shown by the dotted lines 24and 26 at the upstream and downstream ends of the generating region.These short-circuits are minimized or eliminated according to thisinvention and as illustrated in FIG. 2.

Referring to FIG. 2, a relatively high-temperature fluid of severalthousand degrees R but in a non-ionized state is introduced through theinlet 32. The tempe-rature though relatively high (in the order ofA3060" K.) is insufficient to ionize the incoming stream which may beheated air under pressure. Acording to this invention a supply tank 34is provided and may contain a suitable seeding material such as liquidalkali metals or for example a saturated solution of an alkali salt (eg.potassium nitrite). The vseeding material from the supply line 35lpasses through a pump 36 and a suitable valve 38 which can conduct theseeding material to either an injection nozzle 4t) or a wall injectionmanifold 42 or -both or a series of nozzles. The temperature of theWorking fluid and the characteristics of the seed material are such thationization of the seed material will occur at a short distancedownstream of the points of injection and the injectors are located suchthat the ionization will reach equilibrium -at the upstream end 44 ofthe main generating region 46. A suitable magnetic field identified bythe numeral 43 is passed through the generating region and electricalcurrent represented by the lines 50 flows across the electrodes 52 land54. The electrodes 52 and 54 are in turn connected to a suitable load58.

In order to sharply reduce the electrical conductivity of the ow in theregion 60 at the downstream end of the gener-ating region an injectornozzle 62 or a wall injection manifold 64 or a series of nozzles mayprovide for the introduction of an appropriate quenching fluid to thedevice. This quenching fluid may be a coolant (such as Water) which willlower the fluid temperature so that the degree ozf ionization and hencethe electrical conductivity decreases markedly. For appropriate Machnumbers of working iluid flow and for cycles in which the exhaust fluidis not to be used in an auxiliary power generator (eg. a turbine), anadditional advantage may be obtained since this coolant may actuallyincrease the stagnation pressure because of the aerothermopressoreffect. A second mechanism for the reduction of electrical conductivitywould be to introduce a quenching iiuid which has a high electroncollision cross-section. In such a case the electrical conductivity isdecreased although the temperature and hence the degree of ionizationmay be relatively unchanged. The addition of the seeding material and`the coolant may be accomplished by either or both devices shown. As forexample as shown in FIG. 3, an annular manifold 70 may be provideddefining an inner chamber 72 which feeds a fluid out of injectorpassages 74 leading to the interior of the main generating duct. Also asshown in FIGS. 4 and 5, an injector head 8i) may be utilized and thishead may include a number of relatively small passa-ges 82 which are fedfrom a chamber 86 to which fluid is conducted by -a main feed passage8S.

As a result of this invention it is apparent that a very eliicientmaignetogasdynamic electric generator has been provided whereby thelosses due to end effects or shortcircnits are substantially eliminated.

Although several embodiments of 4this invention have been illustratedand described herein, it will be yapparent that various changes may bemade in the construction and arrangement of the various parts withoutldeparting from the scope of the novel concept.

What it is desired by Letters Patent is:

l. A magnetogasdynamic electric generator comprising an elongatedpassage, means for forcing a relatively hightemperature non-ionizedfluid through said passage, means defining a genera-ting region in aportion of said passage, said generating region having upstream anddownstream ends, means for injecting a second fluid into said passageadjacent said upstream end to ionize the liuid at a point substantiallycoincident with the upstream end of said region, means for generating amagnetic electrical field passing through said generating region, meansadjacent said generating region for collecting electrical currentgenerated by the passage of the ionized working fluid through thegenerating region and means for injecting a quenching material into theworking fiuid at a point just prior to the working fluids exit from saidgenerating region to reduce the conductivity of the working fluid.

2. A generator according to claim 1 wherein said second fluid is aliquid metal.

3. A generator according to claim 1 wherein said second fluid is aliquid alkali metal.

4. A magetogasdynamic electric generator comprising an elongatedpassage, means for owing a relatively hightemperature non-ionizedWorking fluid through said passage, means dening a generating region ina portion of said passage, said generating region having upstream anddownstream ends, means for injecting a seeding material into saidpassage adjacent said upstream end to ionize the fluid passing therebyand cause the working fluid to become conductive immediately adjacentsaid upstream end, means for generating a magnetic -eld passing throughsaid generating region, means adjacent said generating region forcollecting electrical current generated by the passage of the ionizedworking lluid through the generating region and means for quenching theworking fluid immediately adjacent the downstream end of said generatingregion to reduce the conductivity of the Working uid.

i5. A generator according to claim 4 wherein said means for injectionand quenching include nozzles in said working fluid.

6. A generator according to claim 4 wherein said means for injection andquenching include nozzles in the wall of said passage.

7. A magnetogasdynamic electric generator comprising an elongatedpassage, means for flowing a relatively hightemperature non-ionized Huidthrough said passage, means defining a generating region in a portion ofsaid passage, said Working region having upstream and downstream ends,means for injecting a second fluid into said passage adjacent saidupstream end to ionize the uid immediately adjacent said upstream and,means for generating a magnetic field passing through said generatingregion, means adjacent said generating region for collecting electrical4- current generated by the passage of the ionized working fluid throughthe generating region, and means for injecting a quenching fluidimmediately adjacent but upstream of said downstream end to decrease theionization of the fluid stream.

8. In a magnetohydrodynamic generator, apparatus for reducing shortcircuit end effects adjacent the downstream terminal point of oppositelydisposed electrodes located within a duct for conveying a hot,electrically conductive comprising: means for introducing anonconducting fluid gas through a magnetic field at an angle to saidelectrodes into said duct at about the downstream terminal point of saidelectrodes whereby the conductivity of at least a portion of said gas isreduced.

References Cited by the Examiner UNITED STATES PATENTS 1,717,413 6/ 1929Rudenberg 310-11 X 2,754,442 7/ 1956 Boutry 313-63 FOREIGN PATENTS1,161,079 3/ 1958 France.

OTHER REFERENCES Publication: Power Design and Equipment ApplicationSection, November 1959, pp. 62 and 64.

Publication: Fundamental Processes of Electrical Discharge in Gases, byLoeb, John Wiley & Sons (1941), pp. 374 to 377, inclusive.

Publication: MHD Power Generation Using Nuclear Fuel, by Avco EverettResearch Laboratory, March 1960, pages 6 and 16.

MILTON Q. HIRSHFIELD, Primary Examiner.

D. X. SLINEY, Examiner.

1. A MAGNETOGASDYNAMIC ELECTRIC GENERATOR COMPRISING AN ELONGATEDPASSAGE, MEANS FOR FORCING A RELATIVELY HIGHTEMPERATURE NON-IONIZEDFLUID THROUGH SAID PASSAGE, MEANS DEFINING A GENERATING REGION IN APORTION OF SAID PASSAGE, SAID GENERATING REGION HAVING UPSTREAM ANDDOWNSTREAM ENDS, MEANS FOR INJECTING A SECOND FLUID INTO SAID PASSAGEADJACENT SAID UPSTREAM END TO IONIZE THE FLUID AT A POINT SUBSTANTIALLYCOINCIDENT WITH THE UPSTREAM END OF SAID REGION, MEANS FOR GENERATING AMAGNETIC ELECTRICAL FIELD PASSING THROUGH SAID GENERATING REGION, MEANSADJACENT SAID GENERATING REGION FOR COLLECTING ELECTRICAL CURRENTGENERATED BY THE PASSAGE OF THE IONIZED WORKING FLUID THROUGH THEGENERATING REGION AND MEANS FOR INJECTING A QUENCHING